Does everybody have a pair of emergency underpants? You know, the undies that are not actually unwearable, but are far from preferable? Not actually falling apart, but maybe the elastic’s stretched just a teensy bit too far, or they were a new brand you purchased that didn’t turn out to be as comfortable as your “old reliable” brand.
You don’t want to chuck them out, so you keep them as the emergency undies. You’d rather not wear them when there’s others available, but when the laundry schedule goes all screwy and there’s nothing else available, they’re certainly better than nothing.
(Ladies may also have an emergency bra.)
At the other end of the spectrum are the favourites. Exceptionally comfortable, perhaps, or just deemed to be lucky. Yes, the lucky undies. Alas, their very status works against them, as through wear and tear, they gradually descend to the status of emergency-only.
You go out and buy some more, and the cycle begins again.